1. Field of the Invention
This invention relates to a wireless communications system or the like that performs wireless communication between base station equipment and a plurality of communications station units, and particularly to technology that achieves a good assignment of groups in a composition wherein each of the communications station units is assigned to a group that defines the receive time band and send time band, and the receive time band and send time band of each communications station unit are made to be different, thereby achieving a good allocation of groups.
In addition, this invention relates to a wireless communications system or the like that performs wireless communication between base station equipment and a plurality of communications station units, and particularly to technology that achieves a good assignment of groups in a composition wherein each of the communications station units is assigned to a group that defines the receive time band and send time band, and the receive time band and send time band of each communications station unit are made to be different, thereby improving the efficiency of data communication.
2. Description of the Prior Art
In recent years, subscriber wireless access systems that utilize wireless communication called Wireless Local Loop (WLL) or Fixed Wireless Access (FWA) or the like have been developed and put into practical application. In addition, with the popularity of the Internet, the need for high-speed, large-capacity communication over wireless media has heightened.
In the aforementioned subscriber wireless access systems, base station equipment (BSE) connected to a public circuit network or other backbone network is installed in a fixed location on the top of a building or tower or other high place, while customer premises equipment (CPE) is also installed in a fixed location on the roof of the customer's building or other high place. The customer premises equipment also includes personal computers (PCs) or other communications terminal units and such communications terminal units connected via a local area network (LAN).
Here, the base station equipment and customer premises equipment may each consist of an outdoor unit (ODU) installed in a fixed location on a building roof, tower or other high place and an indoor unit (IDU) installed in a fixed location within a building or the like, and these are connected with a cable. In addition, the outdoor unit of the base station equipment and customer premises equipment is equipped with a wireless processor that performs the processing of wireless communication using an antenna, mainly controlling the processing of wireless communication. In addition, the indoor unit of the base station equipment mainly controls data communication with the backbone network, while the indoor unit of the customer premises equipment mainly controls data communication with the communications terminal units or LAN or the like.
In addition, in the aforementioned subscriber wireless access systems, wireless communication is performed between the base station equipment and customer premises equipment by means of a time-division multiplexing communications protocol using wireless frames. It is thus possible to connect to and perform data communication among the LANs or the like connected to different customer premises equipment covered by the same base station equipment, and also connect to and perform data communication with LANs or the like connected to other customer premises equipment connected to the backbone network connected to the base station equipment.
Here follows a description of an example of the composition of a typical communication frame used in P-MP (Point-Multi Point) wireless communication conducted between base station equipment and customer premises equipment at a plurality of locations in the aforementioned subscriber wireless access systems.
First, in reference to FIGS. 10(a) to 10(f), we shall present an example of the composition of such communication frames.
Note the figure shows an example of the communications protocol in the case of performing wireless communication covering base station equipment at one location (the “base station”) and customer premises equipment at two locations (“customer premises 1” and “customer premises 2”).
FIG. 10(a) shows an example of the composition of the downlink frames in downlink communication from the base station equipment to the customer premises equipment. These downlink frames consist of the unit frames, the “first frame,” “second frame,” “third frame” . . . , each of which consisting of one broadcast control channel (BCCH), two downlink-only short data channels (SD1, SD2) and one downlink-only long data channel (LD1).
Here, the BCCH is a downlink traffic channel for achieving synchronization between the base station equipment and customer premises equipment, and for giving permission for data communication from the base station equipment to the customer premises equipment. The SD (SD1 and SD2) is a downlink traffic channel for sending short data from the base station equipment to the customer premises equipment. The LD (LD1) is a downlink traffic channel for sending long data from the base station equipment to the customer premises equipment.
In addition, FIG. 10(b) shows an example of the composition of the uplink frames in uplink communication from the customer premises equipment to the base station equipment. These uplink frames consist of the unit frames, the “first frame,” “second frame,” “third frame” . . . , each of which consisting of one link control channel (LCCH), two uplink-only short data channels (SU1, SU2) and one uplink-only long data channel (LU1).
Here, the LCCH is an uplink traffic channel for making a request for data communication from the customer premises equipment to the base station equipment. The SU (SU1 and SU2) is an uplink traffic channel for sending short data from the customer premises equipment to the base station equipment. The LU (LU1) is an uplink traffic channel for sending long data from the customer premises equipment to the base station equipment.
In addition, as shown in FIGS. 10(a) and (b), the downlink frames shown in FIG. 10(a) and the uplink frames shown in FIG. 10(b) are configured such that the two unit frames for each of the unit frames called the “first frame,” “second frame,” “third frame,” . . . are disposed in the same time band. In each unit frame, BCCH and LCCH are disposed in the same time band, while SD1 and SU1 are disposed in the same time band, and LD1 and LU1 are also disposed in the same time band.
Moreover, when such communication frames are used, because of the composition of communication frames, sending and receiving are performed simultaneously in the base station equipment, and sending and receiving are also performed simultaneously in the customer premises equipment.
Specifically, as shown in FIGS. 10(a) and (b), the base station equipment uses the BCCH to send synchronization information and the like to the customer premises equipment in each unit frame. SD1, SD2 and LD1 are used to send data to the customer premises equipment. The LCCH is used to receive send requests from the customer premises equipment while SU1, SU2 and LU1 are used to receive data from the customer premises equipment.
On the other hand, as shown in FIGS. 10(c), (d), (e) and (f), the customer premises equipment uses the BCCH to receive synchronization information and the like from the base station equipment in each unit frame. SD1, SD2 and LD1 are used to receive data from the base station equipment. The LCCH is used to send send requests to the base station equipment while SU1, SU2 and LU1 are used to send data to the base station equipment. Note that SU1, SU2 and LU1 are used by the customer premises equipment permitted by the base station equipment to send data, and in the customer premises equipment in question, these data channels are used to perform the sending of data to the base station equipment.
In addition, in reference to FIG. 11, we shall present another example of the composition of typical communication frames used in P-MP wireless communication performed between base station equipment and customer premises equipment at a plurality of locations in the aforementioned subscriber wireless access systems.
Note the figure shows an example of the communications protocol in the case of performing wireless communication covering base station equipment at one location (the “base station”) and customer premises equipment at two locations (“customer premises 1” and “customer premises 2”).
FIG. 11(a) shows an example of the composition of the downlink frames in downlink communication from the base station equipment to the customer premises equipment. These downlink frames consist of a plurality of the unit frames, the “first frame,” “second frame,” “third frame” . . . , each of which consisting of one broadcast control channel (BCCH), one downlink-only short data channel (SD) and one downlink-only long data channel (LD).
In addition, FIG. 11(b) shows an example of the composition of the uplink frames in uplink communication from the customer premises equipment to the base station equipment. These uplink frames consist of the unit frames, the “first frame,” “second frame,” “third frame” . . . , each of which consisting of one link control channel (LCCH), one uplink-only short data channel (SU) and one uplink-only long data channel (LU).
In this manner, the composition of the communication frames shown in this figure is identical to the composition of the communication frames shown in FIG. 10 above except that there is only one short data channel (SD, SU) in each unit frame, for example. Moreover, even in the case that such communication frames are used, because of the composition of communication frames, sending and receiving are performed simultaneously in the base station equipment as shown in FIGS. 11(a) and (b), and sending and receiving are also performed simultaneously in the customer premises equipment as shown in FIGS. 11(c), (d), (e) and (f).
However, in a subscriber wireless access system wherein wireless communication is performed between base station equipment and customer premises equipment at a plurality of locations using communication frames such as those shown in the aforementioned FIGS. 10(a) to 10(f) and FIGS. 11(a) to 11(f), it is necessary to perform sending and receiving simultaneously not only by the base station equipment, but also by the customer premises equipment which is required to have an inexpensive composition. Problems occur, for example, when common send/receive blocks cannot be provided from a hardware standpoint, so the customer premises equipment becomes expensive, and the power consumed by the customer premises equipment becomes large.
The present invention is intended to solve such problems and propose wireless communication using communication frames whereby, the wireless frames themselves are given definitions regarding groups which are sets of customer premises equipment and thus each unit of customer premises equipment does not access the base station equipment with sending and receiving simultaneously. However, in a subscriber wireless access system wherein wireless communication is performed with each of the plurality of units of customer premises equipment assigned to one of the groups among the plurality of groups in this manner, it is necessary to perform adequate study regarding how the assignment of groups is to be performed. To wit, the frequency of occurrence of data received by each unit of customer premises equipment is normally different from the frequency of occurrence of data sent and thus the data flow is asymmetric, so differences occur in the usage of wireless channels between the downlink and uplink, and thus differences occur in the overall system throughput depending on how the groups are assigned.
In addition, the frequency of occurrence of the short data and long data received on the downlink and the frequency of occurrence of the short data and long data sent on the uplink of each unit of customer premises equipment can fluctuate depending on the traffic situation, so differences occur in the usage of wireless channels between the downlink and uplink, and thus differences occur in the overall system throughput depending on how the groups are assigned.
The present invention came about in order to solve the aforementioned problems in the prior art, and has as its object to provide a wireless communications system that is able to increase the system throughput by adopting a protocol wherein each communications station unit is assigned to a group and the sending time band and receiving time band are made different for each communications station unit, and thus, at the time that wireless communication is performed between a base station unit and a plurality of communications station units, a good assignment of groups is achieved.
In addition, in the aforementioned conventional subscriber wireless access system, sufficient study had not been made on the point of improving the efficiency of data communication. Specifically, because the wireless bandwidth is limited and guard time containing no radio signals, a preamble, unique word and the like are inserted at the beginning of each data channel, when the region for sending data is divided in a fixed manner as described above into the SD1 (or SU1), SD2 (or SU2), LD1 (or LU1) to obtain a frame composition with such a data channel composition, there are problems in that the utilization of the communication bandwidth is limited depending on the data content.
The present invention came about in order to solve the aforementioned problems in the prior art, and has as its object to provide a wireless communications system that is able to increase the efficiency of data communication by adopting a protocol wherein each communications station unit is assigned to a group and the sending time band and receiving time band are made different for each communications station unit at the time that wireless communication is performed between a base station unit and a plurality of communications station units.